Fabrication of a pair of vertical fin field effect transistors having a merged top source/drain

ABSTRACT

A method of fabricating a vertical fin field effect transistor with a merged top source/drain, including, forming a source/drain layer at the surface of a substrate, forming a plurality of vertical fins on the source/drain layer; forming protective spacers on each of the plurality of vertical fins, forming a sacrificial plug between two protective spacers, forming a filler layer on the protective spacers not in contact with the sacrificial plug, and selectively removing the sacrificial plug to form an isolation region trench between the two protective spacers.

BACKGROUND Technical Field

The present invention generally relates to adjacent vertical fin fieldeffect transistors (FinFETs) having a merged top source/drain, and moreparticularly to fabricating two vertical fin field effect transistorselectrically coupled through a merged top source/drain.

Description of the Related Art

A Field Effect Transistor (FET) typically has a source, a channel, and adrain, where current flows from the source to the drain, and a gate thatcontrols the flow of current through the channel. Field EffectTransistors (FETs) can have a variety of different structures, forexample, FETs have been fabricated with the source, channel, and drainformed in the substrate material itself, where the current flowshorizontally (i.e., in the plane of the substrate), and FinFETs havebeen formed with the channel extending outward from the substrate, butwhere the current also flows horizontally from a source to a drain. Thechannel for the FinFET can be an upright slab of thin rectangularsilicon (Si), commonly referred to as the fin with a gate on the fin, ascompared to a MOSFET with a single gate in the plane of the substrate.Depending on the doping of the source and drain, an n-FET or a p-FET canbe formed.

Examples of FETs can include a metal-oxide-semiconductor field effecttransistor (MOSFET) and an insulated-gate field-effect transistor(IGFET). Two FETs also can be coupled to form a complementary metaloxide semiconductor (CMOS) device, where a p-channel MOSFET andn-channel MOSFET are coupled together.

With ever decreasing device dimensions, forming the individualcomponents and electrical contacts becomes more difficult. An approachis therefore needed that retains the positive aspects of traditional FETstructures, while overcoming the scaling issues created by formingsmaller device components.

SUMMARY

In accordance with an embodiment of the present invention, a method offabricating adjacent vertical fin field effect transistors with a mergedtop source/drain is provided. The method includes forming a source/drainlayer at the surface of a substrate, forming a plurality of verticalfins on the source/drain layer. The method further includes formingprotective spacers on each of the plurality of vertical fins. The methodfurther includes forming a sacrificial plug between two protectivespacers. The method further includes forming a filler layer on theprotective spacers not in contact with the sacrificial plug, andselectively removing the sacrificial plug to form an isolation regiontrench between the two protective spacers.

In accordance with another embodiment of the present invention, a methodof fabricating two vertical fin field effect transistors electricallycoupled through a merged top source/drain is provided. The methodincludes forming a source/drain layer on a substrate, forming at leastfour vertical fins on the source/drain layer. The method furtherincludes forming an isolation region through the source/drain layer toseparate the source/drain layer into a first bottom source/drain and asecond bottom source/drain, wherein at least two of the least fourvertical fins are on the first bottom source/drain, and at least two ofthe least four vertical fins are on the second bottom source/drain. Themethod further includes forming a top source/drain on each of the atleast four vertical fins, wherein the top source/drains are formed to asize that is sufficient for at least two top source/drains to coalesceinto a merged source/drain.

In accordance with another embodiment of the present invention, anadjoined pair of vertical fin devices is provided. The adjoined pair ofvertical fin devices includes a first bottom source/drain and a secondbottom source/drain on a substrate, wherein the first bottomsource/drain is separated from the second bottom source/drain by ashallow trench isolation region in the substrate. The adjoined pair ofvertical fin devices further includes at least four vertical fins,wherein at least two of the at least four vertical fins are on the firstbottom source/drain and at least two of the at least four vertical finsare on the second bottom source/drain. The adjoined pair of vertical findevices further includes a gate structure on each of the at least fourvertical fins. The adjoined pair of vertical fin devices furtherincludes a top source/drain on at least one of the at least two verticalfins on the first bottom source/drain, a top source/drain on at leastone of the at least two vertical fins on the second bottom source/drain,and a merged source/drain on one vertical fin on the first bottomsource/drain and one adjacent vertical fin on the second bottomsource/drain that bridges the shallow trench isolation region toelectrically couple the adjacent vertical fins.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description will provide details of preferred embodimentswith reference to the following figures wherein:

FIG. 1 is a cross-sectional side view showing a substrate, in accordancewith an embodiment of the present invention;

FIG. 2 is a cross-sectional side view showing a bottom source/drainlayer at the surface of the substrate, a vertical fin layer on thebottom source/drain layer, a hardmask layer on the vertical fin layer, asacrificial mandrel layer and a template layer on the hardmask layer, inaccordance with an embodiment of the present invention;

FIG. 3 is a cross-sectional side view showing a plurality of verticalfins with a hardmask cap on each vertical fin, in accordance with anembodiment of the present invention;

FIG. 4 is a cross-sectional side view showing remaining vertical finsafter selective removal of intervening vertical fin(s) by a fin cutprocess, in accordance with an embodiment of the present invention;

FIG. 5 is a cross-sectional side view showing a protective cover formedon the plurality of vertical fins and hardmask caps, in accordance withan embodiment of the present invention;

FIG. 6 is a cross-sectional side view showing protective spacers formedon the vertical fins and a portion of the hardmask caps after anetch-back process, in accordance with an embodiment of the presentinvention;

FIG. 7 is a cross-sectional side view showing a pinch-off layer formedon the protective spacers, hardmask caps, and exposed portions of thesource/drain layer, in accordance with an embodiment of the presentinvention;

FIG. 8 is a cross-sectional side view showing a sacrificial plug betweentwo protective spacers on vertical fins after etching back portions ofthe pinch-off layer, in accordance with an embodiment of the presentinvention;

FIG. 9 is a cross-sectional side view showing a filler layer on theprotective spacers, hardmask caps, and sacrificial plug, in accordancewith an embodiment of the present invention;

FIG. 10 is a cross-sectional side view showing the filler layer andsacrificial plug after a chemical-mechanical polishing (CMP), inaccordance with an embodiment of the present invention;

FIG. 11 is a cross-sectional side view showing an isolation regiontrench formed between two opposing protective spacers on adjacentvertical fins by removal of the sacrificial plug, in accordance with anembodiment of the present invention;

FIG. 12 is a cross-sectional side view showing the isolation regiontrench extended through the source/drain layer and into a portion of theunderlying substrate, in accordance with an embodiment of the presentinvention;

FIG. 13 is a cross-sectional side view showing exposed vertical finsafter removal of the filler layer, protective spacers, and hardmaskcaps, in accordance with an embodiment of the present invention;

FIG. 14 is a cross-sectional side view showing a dummy layer coveringthe vertical fins, source/drain layer segments, and forming a fill inthe isolation region trench, in accordance with an embodiment of thepresent invention;

FIG. 15 is a cross-sectional side view a showing masking layer on an ILDlayer, in accordance with an embodiment of the present invention;

FIG. 16 is a cross-sectional side view showing isolation region trenchesformed into the substrate on both sides of the initial isolation regiontrench, in accordance with an embodiment of the present invention;

FIG. 17 is a cross-sectional side view showing the isolation regiontrenches and vertical fins after removal of the ILD layer and maskinglayer or the OPL, in accordance with an embodiment of the presentinvention;

FIG. 18 is a cross-sectional side view showing a trench fill layer onthe vertical fins and bottom source/drains, and in the isolation regiontrenches, in accordance with an embodiment of the present invention;

FIG. 19 is a cross-sectional side view showing filled shallow trenchisolation regions in the substrate adjacent to bottom source/drains, inaccordance with an embodiment of the present invention;

FIG. 20 is a cross-sectional side view showing a bottom spacer and agate structure formed on each of the vertical fins, bottomsource/drains, and shallow trench isolation regions, in accordance withan embodiment of the present invention;

FIG. 21 is a cross-sectional side view showing an ILD layer onconfigured gate structures, in accordance with an embodiment of thepresent invention;

FIG. 22 is a cross-sectional side view showing a top spacer layer on theILD layer and vertical fins, in accordance with an embodiment of thepresent invention;

FIG. 23 is a cross-sectional side view showing top source/drains formedon the upper portion of the vertical fins, in accordance with anembodiment of the present invention; and

FIG. 24 is a cross-sectional side view showing a second ILD layer formedon the top source/drains and top spacer layer, in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION

Principles and embodiments of the present invention relate generally toavoiding first level metallic interconnects between adjacent FinFETs byfabricating top source/drains on vertical fins that merge into a singletop source/drain that spans the two vertical fins. Typically, differentelectrical contacts are formed to the top source/drain on each verticalfin, and interconnecting the electrical contacts through a metallizationlayer. By epitaxially growing the top source/drain until two separatetop source/drains amalgamate into a merged source/drain, additionalsteps and metallization connects can be avoided.

In addition, a self-aligned isolation region can be formed between thetwo coupled FinFET devices, where the isolation region can beself-aligned with the gate structures on the adjacent devices, and themerged top source/drain can bridge the isolation region to electricallycouple the adjacent vertical fins. The self-aligned isolation region(e.g. shallow trench isolation (STI) region) can be adjacent to and incontact with spacers on the sidewalls of a vertical fin, where thethickness of the spacer(s) can determine the distance of the isolationregion from the vertical fin(s). The gate lengths on both sidewalls of avertical fin can be the same, and the gate lengths on two adjacentvertical fins can be the same, where increased consistency of the gatelengths can improve device performance.

Principles and embodiments of the present invention also relate to useof a pinch-off layer to locate a sacrificial plug between two closelyspaced vertical fins to align the isolation region with the two verticalfins and gate structures formed thereon. Control of different distancesbetween a plurality of vertical fins and/or selective fin removal canprovide closer spacing between vertical fins intended to be electricallycoupled through the merged source/drains, and greater spacing betweenother fins forming the FinFET device, such that the closer fins areproperly spaced for the top source/drains to amalgamate before the othertop source/drains grow to a size that shorts the neighboring verticalfins that are farther apart.

Exemplary applications/uses to which the present invention can beapplied include, but are not limited to: vertical FinFETs, complementarymetal-oxide-semiconductor (CMOS) field effect transistors, digital logicgates (e.g., NAND, NOR, XOR, etc.) and memory devices (e.g., DRAM, SRAM,etc.).

In various embodiments, the materials and layers can be deposited byphysical vapor deposition (PVD), chemical vapor deposition (CVD), atomiclayer deposition (ALD), molecular beam epitaxy (MBE), or any of thevarious modifications thereof, for example, plasma-enhanced chemicalvapor deposition (PECVD), metal-organic chemical vapor deposition(MOCVD), low pressure chemical vapor deposition (LPCVD), electron-beamphysical vapor deposition (EB-PVD), and plasma-enhanced atomic layerdeposition (PEALD). The depositions can be epitaxial processes, and thedeposited material can be crystalline. In various embodiments, formationof a layer may be by one or more deposition processes, where, forexample, a conformal layer can be formed by a first process (e.g., ALD,PEALD, etc.) and a fill can be formed by a second process (e.g., CVD,electrodeposition, PVD, etc.).

Reference to source/drain projections, layers, regions, etc., isintended to indicate that the particular device feature can beimplemented as a source or a drain except as expressly indicatedotherwise. In addition, the role of source and drain for an activedevice can in some instances be reversed, so a previously indicateddrain may instead be a source and vice versa. Reference to asource/drain is, therefore, intended to encompass the broadestreasonable scope of the term.

It is to be understood that aspects of the present invention will bedescribed in terms of a given illustrative architecture; however, otherarchitectures, structures, substrate materials and process features andsteps can be varied within the scope of aspects of the presentinvention.

It should be noted that certain features may not be shown in all figuresfor the sake of clarity. This is not intended to be interpreted as alimitation of any particular embodiment, or illustration, or scope ofthe claims.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, a cross-sectional side viewof a substrate is shown, in accordance with an embodiment of the presentinvention.

In one or more embodiments, a substrate 110 can be a semiconductor or aninsulator, or a combination of semiconductor and insulator with anactive surface layer (ASL) made of a semiconductor material at thesubstrate surface. Various portions of the substrate 110 can becrystalline, semi-crystalline, microcrystalline, or amorphous. Thesubstrate can be essentially (i.e., except for contaminants) a singleelement (e.g., silicon), primarily (i.e., with doping) of a singleelement, for example, silicon (Si) or germanium (Ge), or the substratecan include a compound, for example, Al₂O₃, SiO₂, GaAs, SiC, or SiGe. Invarious embodiments, the substrate can include a carrier portion thatcan be polycrystalline or amorphous, or an insulating material (e.g.glass, Al₂O₃, SiC, etc.) and an active surface layer that is a singlecrystal semiconductor material.

In one or more embodiments, the substrate 110 can have multiple materiallayers, for example, a semiconductor-on-insulator substrate (SeOI), asilicon-on-insulator substrate (SOI), germanium-on-insulator substrate(GeOI), or silicon-germanium-on-insulator substrate (SGOI), where anactive surface semiconductor layer of the substrate 110 can be on asubstrate insulator layer (e.g., buried oxide layer (BOX)). Thesubstrate 110 can also have other layers forming the substrate,including high-k oxides and/or nitrides. The substrate 110 can also haveother device structures such as isolation regions (not shown). In one ormore embodiments, a substrate insulator layer (e.g., BOX layer) can beformed on at least a portion of a substrate 110.

In various embodiments, the substrate 110 may be a single crystalsilicon (Si), silicon-germanium (SiGe), or III-V semiconductor (e.g.,GaAs) wafer, or have a single crystal silicon (Si), silicon-germanium(SiGe), or III-V semiconductor (e.g., GaAs) active surface layer. In oneor more embodiments, the substrate 110 can be a single crystal siliconwafer.

In various embodiments, the substrate can be n-doped (e.g., withphosphorous, arsenic, antimony, etc.) or p-doped (e.g., with boron,gallium, indium, etc.), where the substrate dopant can be acounter-dopant for a bottom source/drain dopant type.

FIG. 2 is a cross-sectional side view showing a bottom source/drainlayer at the surface of the substrate, a vertical fin layer on thebottom source/drain layer, a hardmask layer on the vertical fin layer, asacrificial mandrel layer and a template layer on the hardmask layer, inaccordance with an embodiment of the present invention.

In one or more embodiments, a bottom source/drain layer 120 can beformed at the surface of the substrate 110, where the bottom sourcedrain layer 120 may be formed from the substrate surface material (e.g.,through dopant implantation) or formed on the substrate surface (e.g.,by epitaxial growth and in situ or ex situ dopant implantation).

In various embodiments, the bottom source/drain layer 120 can be formedby epitaxial growth on an exposed portion of the substrate 110, and/ordopants can be implanted into the bottom source/drain layer 120. Thebottom source/drain layer 120 can be in-situ doped (where doping andepitaxy growth are performed at the same time), and/or ex-situ doped(where doping occurs before and/or after epitaxy). Dopants can beincorporated during epitaxy or by other suitable doping techniques,including but not limited to, ion implantation, gas phase doping, plasmadoping, plasma immersion ion implantation, cluster doping, infusiondoping, liquid phase doping, solid phase doping, etc. In variousembodiments, the bottom source/drain layer 120 can be doped to formn-type or p-type source/drains to fabricate NFETs or PFETs.

In one or more embodiments, a vertical fin layer 130 can be formed onthe bottom source/drain layer 120, where a crystalline vertical finlayer can be epitaxially grown on a crystalline bottom source/drainlayer 120 having a predetermined crystal orientation. The vertical finlayer 130 can be a crystalline semiconductor material.

In one or more embodiments, the vertical fin layer 130 can be silicon orsilicon-germanium, where the vertical fin layer can be strained orunstrained depending on the amount of lattice mismatch between thematerial of the vertical fin layer 130 and the material of the bottomsource/drain layer 120 and/or substrate 110.

In one or more embodiments, a hardmask layer 140 can be formed on thevertical fin layer 130, where the hardmask layer 140 can be patterned toform masks for forming one or more vertical fins.

In one or more embodiments, the hardmask layer 140 can be silicon oxide(SiO), silicon nitride (SiN), a silicon oxynitride (SiON), a siliconcarbonitride (SiCN), a silicon boronitride (SiBN), a silicon borocarbide(SiBC), a silicon boro carbonitride (SiBCN), a boron carbide (BC), aboron nitride (BN), or combinations thereof.

In one or more embodiments, a sacrificial mandrel layer 150 may beformed on at least a portion of the hardmask layer 140. The sacrificialmandrel layer 150 may be a semiconductor material, for example,amorphous silicon (a-Si), polycrystalline silicon (p-Si),microcrystalline silicon (m-Si), amorphous carbon (a-C), or combinationsthereof.

In one or more embodiments, a template layer 155 can be formed on thesacrificial mandrel layer 150, where the template layer 155 can be alithography resist material, for example, an photoresist material or ane-beam resist material (e.g., poly methylmethacralate (PMMA), hydrogensilsequioxane (HSQ), etc.). In various embodiments, the template layer155 can be spun onto the surface of the sacrificial mandrel layer 150.

FIG. 3 is a cross-sectional side view showing a plurality of verticalfins with a hardmask cap on each vertical fin, in accordance with anembodiment of the present invention.

In one or more embodiments, a vertical fin 131 can be formed on asubstrate 110. In various embodiments, the vertical fins 131 can beetched into the vertical fin layer 130 on the bottom source/drain layer120 by employing a lithographic patterning process, a sidewall imagetransfer (SIT) process, or epitaxially grown on the substrate. Thevertical fin 131 can be formed by a SIT process (i.e., self-aligneddouble patterning (SADP)), or double sidewall image transfer process(e.g., self-aligned quadruple patterning (SAQP)), as would be known inthe art.

In one or more embodiments, the template layer 155 may be formed on atleast a portion of the sacrificial mandrel layer 150, where the templatelayer 155 may be a soft mask that can be patterned and developed to formopening(s) and mask feature(s). In various embodiments, the templatelayer 155 can be patterned and developed to form one or more mandreltemplates that cover a portion of the sacrificial mandrel layer 150,while exposing other portions of the sacrificial mandrel layer 150.

In one or more embodiments, a plurality of sacrificial mandrels can beformed from the sacrificial mandrel layer 150, where an anisotropic etchmay be used to form the sacrificial mandrels. An anisotropic etch may bea dry plasma etch, for example, a reactive ion etch (RIE), thatpreferentially removes material from the sacrificial mandrel layer 150in a direction normal to the surface, while limiting etching of thesidewalls. The plurality of sacrificial mandrels may act as templatesfor forming spacers for the SIT process.

In one or more embodiments, the sacrificial mandrels may have a width inthe range of about 5 nm to about 60 nm, or in the range of about 10 nmto about 40 nm, where the width of a sacrificial mandrel can define thedistance, D₁, between two spacers, and thereby, two subsequently formedadjacent vertical fins 131. A distance, D₂, between two vertical fins131 separated by a single intervening vertical fin 131 can be twice thedistance D₁ plus the width, W, of the intervening vertical fin (i.e.,(2×D₁)+W).

It should be noted that distances D₁ and D₂ are measured between facingsurfaces of the vertical fins 131, whereas pitch is the distancemeasured between the same face of the vertical fins.

In one or more embodiments, the plurality of sacrificial mandrels mayhave a pitch between adjacent sacrificial mandrels different from thewidth of the sacrificial mandrels. The pitch between adjacentsacrificial mandrels may be in the range of about 20 nm to about 200 nm,or in the range of about 70 nm to about 120 nm, or in the range of about24 nm to about 80 nm, or in the range of about 35 nm to about 100 nm,where the pitch between sacrificial mandrels can control the distancebetween spacers on the adjacent sacrificial mandrels, and thereby, thedistance, D₂ between vertical fins 131 separated by an intervening fin.

In one or more embodiments, one or more spacer layer(s) may be formed onone or more of the sacrificial mandrels. The spacer layer(s) can beformed by a blanket deposition over the sacrificial mandrels and exposedportions of the surface of the hardmask layer 140, where the blanketdeposition may be a conformal deposition, for example by ALD, CVD, or acombination thereof. The thickness of the spacer layers can bepredetermined to control the width, W, of the subsequently formedvertical fins 131, and to vary the pitch between fin templates byintroducing additional spacer layers to provide variably spaced verticalfins. Using an SIT process or double SIT process provides chemicalprocess control over critical dimension (CD) resolution (e.g., monolayerthickness resolution for ALD) in place of optical resolution limits oncritical dimensions.

In one or more embodiments, the spacer layer may have a thickness in therange of about 3 nm to about 25 nm, or in the range of about 5 nm toabout 20 nm, where the thickness of the spacer layer can determine thewidth of the vertical fins 131.

In one or more embodiments, the sacrificial mandrels can be removed toform a plurality of free-standing spacers, where the spacers may have afirst pitch controlled by the spacer width and width of the sacrificialmandrels, and a second pitch controlled by the pitch of the sacrificialmandrels, such that the free standing spacers can be shifted closer toor further from a neighboring spacer. The sacrificial mandrels can beremoved by a selective isotropic etch that removes the material of thesacrificial mandrels without notably effecting the spacers or hardmasklayer 140.

In various embodiments, the pattern of the spacers can be transferred tothe hardmask layer 140, by a directional etch to form hardmask caps 141.The portions of the vertical fin layer between the hardmask caps 141 andspacers can be removed by a directional etch, for example, a reactiveion etch or a neutral beam etch (NBE).

In one or more embodiments, one or more vertical fin(s) 131 can beformed from the vertical fin layer 130 using the spacers and/or hardmaskcaps 141 formed from the hardmask layer 140 as templates. In variousembodiments, the spacers may be removed prior to formation of thevertical fins 131, and the hardmask caps 141 may be used to mask thevertical fin layer 130 for etching.

In various embodiments, each of the one or more vertical fin(s) 131 canbe formed on a portion of the underlying source/drain layer 120, wherethe source/drain layer may form a source/drain for one or more of thevertical fin(s) 131.

In one or more embodiments, the vertical fin 131 can be formed on thesource/drain layer 120, where the vertical fin 131 can be a strainedvertical fin made of a semiconductor material. The vertical fin 131 canhave a tensile or compressive strain. In some embodiments, the strain inthe vertical fin 131 ranges from 0.3% to 1.5%, although fins withgreater or less strain can also be employed.

FIG. 4 is a cross-sectional side view showing remaining vertical finsafter selective removal of intervening vertical fin(s) by a fin cutprocess, in accordance with an embodiment of the present invention.

In one or more embodiments, the distances, D₁ and D₂, between adjacentvertical fins 131 can be further adjusted using a fin cut process toremove certain predetermined vertical fins 131 to form a larger space(e.g., 2×, 3×, 4×, etc. the fin pitch) between vertical fins. In variousembodiments, one or more vertical fins 131 can be removed throughmasking and etching, as would be known in the art for a fin cut process.A remaining vertical fin can have a distance, D₂, to a first adjacentfin 131, and a distance, D₁, to a second adjacent fin. The distance, D₂,can be larger than the distance, D₁. The distance, D₁, can be thesmallest distance between two immediately adjacent fins 131.

In one or more embodiments, the distance, D₁, between two adjacentvertical fins can be in the range of about 10 nm to about 40 nm, or inthe range of about 10 nm to about 25 nm, although other distances arealso contemplated.

In one or more embodiments, the distance, D₂, between two adjacentvertical fins can be in the range of about 30 nm to about 100 nm, or inthe range of about 40 nm to about 100 nm, or in the range of about 50 nmto about 75 nm, although other distances are also contemplated.

FIG. 5 is a cross-sectional side view showing a protective cover formedon the plurality of vertical fins and hardmask caps, in accordance withan embodiment of the present invention.

In one or more embodiments, a protective cover 160 can be formed on theexposed top surface and sides of the hardmask caps 141, and sidewallsand end faces of the one or more vertical fin(s) 131 formed on thesource/drain layer 120, where the protective cover 160 can be formed bya blanket deposition. In various embodiments, the protective cover 160can be formed on the hardmask caps 141, vertical fins 131, and exposedsurface of the source/drain layer 120 by a conformal deposition, forexample, ALD or PEALD, such that the thickness of the protective covercan be tightly controlled.

In various embodiments, the protective cover 160 can have an essentiallyuniform thickness (e.g., within process variances/tolerances) on thehorizontal and vertical exposed surfaces.

In one or more embodiments, the protective cover 160 can have athickness, T_(c), in the range of about 3 nm to about 25 nm, or in therange of about 5 nm to about 20 nm, or about 7 nm to about 15 nm.

In one or more embodiments, the protective cover 160 can be siliconoxide (SiO), silicon nitride (SiN), a silicon oxynitride (SiON), asilicon carbonitride (SiCN), a silicon boronitride (SiBN), a siliconborocarbide (SiBC), a silicon boro carbonitride (SiBCN), a boron carbide(BC), a boron nitride (BN), or combinations thereof. The material of theprotective cover can be the same material as the hardmask caps 141, sothe protective cover 160 and hardmask caps 141 can be removed by thesame process. In various embodiments, the protective cover 160 andhardmask caps 141 can be different materials, so the protective covercan be selectively removed without removing the hardmask caps 141.

FIG. 6 is a cross-sectional side view showing protective spacers formedon the vertical fins and a portion of the hardmask caps after anetch-back process, in accordance with an embodiment of the presentinvention.

In one or more embodiments, the protective cover 160 can be removed fromthe horizontal surfaces of the hardmask caps 141 and source/drain layer120, while leaving protective spacers 161 on at least the sidewalls andend faces of the vertical fins 131. A directional etch (e.g., RIE) canbe used to remove the portion of the protective cover 160 from thehorizontal surfaces.

In various embodiments, the thickness of the protective spacers 161 candefine an offset distance from the sidewalls of the vertical fins 131and fill in a portion of the space between adjacent vertical fins. Thethickness of the protective cover 160 can determine the width andposition of a sacrificial plug between two closely spaced vertical fins131.

FIG. 7 is a cross-sectional side view showing a pinch-off layer formedon the protective spacers, hardmask caps, and exposed portions of thesource/drain layer, in accordance with an embodiment of the presentinvention.

In one or more embodiments, a pinch-off layer 170 can be formed on theprotective spacers 161 and source/drain layer 120, where the pinch-offlayer can be blanket deposited (e.g., CVD, PECVD, LPCVD, ALD, PEALD,etc.).

In one or more embodiments, the thickness of the pinch-off layer 170 canbe predetermined to fill the space between two closely spaced (e.g.,having distance D₁) vertical fins 131 to form a sacrificial plug 175,where two portions of the pinch-off layer 170 can coalesce into thesacrificial plug 175.

In one or more embodiments, the pinch-off layer 170 and sacrificial plug175 can be silicon oxide (SiO), silicon nitride (SiN), a siliconoxynitride (SiON), a silicon carbonitride (SiCN), a silicon boronitride(SiBN), a silicon borocarbide (SiBC), a silicon boro carbonitride(SiBCN), a boron carbide (BC), a boron nitride (BN), or combinationsthereof. The material of the pinch-off layer 170 and sacrificial plug175 can be a different material from the protective spacer(s) 161 andhardmask caps 141, so the pinch-off layer 170 and sacrificial plug 175can be selectively etched back, and can be selectively removed frombetween two protective spacers.

FIG. 8 is a cross-sectional side view showing a sacrificial plug betweentwo protective spacers on vertical fins after etching back portions ofthe pinch-off layer, in accordance with an embodiment of the presentinvention.

In one or more embodiments, the pinch-off layer 170 can be uniformlyremoved from the exposed surfaces, such that a sacrificial plug 175remains in the space between two closely spaced vertical fins 131. Anisotropic etch (e.g., wet etch) can be used to remove the thickness ofthe pinch-off layer 170 from the exposed surfaces, where the isotropicetch can be a timed etch. The predetermined thickness of pinch-off layermaterial can be removed to expose the protective spacers 161 andsource/drain layer 120, while only reducing the height of thesacrificial plug 175 between the vertical fins 131 by approximately thematerial thickness. In various embodiments, the height of thesacrificial plug 175 can be greater than the height of the verticalfins.

FIG. 9 is a cross-sectional side view showing a filler layer on theprotective spacers, hardmask caps, and sacrificial plug, in accordancewith an embodiment of the present invention.

In one or more embodiments, a filler layer 180 can be formed on theprotective spacers 161, hardmask caps 141, sacrificial plug 175, andexposed surfaces of the source/drain layer 120, where the filler layercan be blanket deposited on the exposed surfaces. The filler layer canextend above the top surfaces of the hardmask caps 141, protectivespacers 161, and sacrificial plug 175.

In one or more embodiments, the filler layer 180 can be silicon oxide(SiO), silicon nitride (SiN), a silicon oxynitride (SiON), a siliconcarbonitride (SiCN), a silicon boronitride (SiBN), a silicon borocarbide(SiBC), a silicon boro carbonitride (SiBCN), a boron carbide (BC), aboron nitride (BN), or combinations thereof. The material of the fillerlayer 180 can be a different material from the sacrificial plug 175,such that the sacrificial plug 175 can be selectively removed withoutremoving the filler layer 180. In various embodiments, the filler layercan be the same material as the hardmask caps 141 and protective spacers161, so the filler layer 180, hardmask caps 141, and protective spacers161 can be removed at the same time with the same isotropic etch.

FIG. 10 is a cross-sectional side view showing the filler layer andsacrificial plug after a chemical-mechanical polishing (CMP), inaccordance with an embodiment of the present invention.

In one or more embodiments, the height of the excess filler layermaterial, and upper portions of the hardmask caps 141, protectivespacers 161, and sacrificial plug 175 can be reduced using a CMP toprovide a smooth, flat surface. In various embodiments, the portion ofthe hardmask caps 141 that is removed is less than the original heightof the hardmask caps 141, such that the tops of the vertical fins 131are still covered by at least a portion of the hardmask caps 141. Theoriginal height of the sacrificial plug 175 can be greater than thecombined height of the hardmask cap 141 and vertical fin 131 after theCMP, so a crease or divot formed during deposition of the sacrificialplug 175 can be removed by the CMP. The top surface of the sacrificialplug can be exposed after the CMP.

In one or more embodiments, a plurality of vertical fins 131 can be onthe source/drain layer 120 with a protective spacer on each sidewall ofeach vertical fin 131. A sacrificial plug 175 can be between and incontact with at least two opposing protective spacers 161 on adjacentvertical fins 131, and a filler layer can be in the space betweenopposing protective spacers 161 not filled by a sacrificial plug 175. Invarious embodiments, the sacrificial plug 175 can be directly on thesource/drain layer 120 and in direct contact with two opposingprotective spacers 161.

FIG. 11 is a cross-sectional side view showing an isolation regiontrench formed between two opposing protective spacers on adjacentvertical fins by removal of the sacrificial plug, in accordance with anembodiment of the present invention.

In one or more embodiments, the sacrificial plug 175 can be removed,where the sacrificial plug 175 can be removed using a selective etch.The selective etch can be a directional etch (e.g., RIE) or anon-directional isotropic etch (e.g., wet etch). Removal of thesacrificial plug 175 can form an isolation region trench 190 between twoprotective spacers 161, and expose a portion of the underlyingsource/drain layer 120 between two closely spaced vertical fins 131. Invarious embodiments, the isolation region trench can be self-alignedwith the two closely spaced vertical fins 131, and off-set from thevertical fins by the thickness of the opposing protective spacers 161.

FIG. 12 is a cross-sectional side view showing the isolation regiontrench extended through the source/drain layer and into a portion of theunderlying substrate, in accordance with an embodiment of the presentinvention.

In one or more embodiments, the exposed portion of the source/drainlayer 120 can be removed to extend the isolation region trench 190through the source/drain layer 120 at least to the substrate 110.Removal of the portion of the source/drain layer at the bottom of theisolation region trench 190 can separate the source/drain layer into twosegments 121. The exposed portion of the source/drain layer 120 can beremoved using a selective, directional etch, for example, a selectiveRIE.

In one or more embodiments, a portion of the substrate 110 can beremoved from the bottom of the isolation region trench 190 to extent theisolation region trench 190 into the substrate 110. Extension of theisolation region trench 190 into the substrate 110 can furtherelectrically isolate two FinFET device subsequently formed on thesource/drain layer.

In one or more embodiments, the isolation region trench 190 can have awidth in the range of about 10 nm to about 40 nm, or in the range ofabout 20 nm to about 30 nm, although other widths are also contemplated.

In one or more embodiments, the isolation region trench 190 can extendinto the substrate 110 by a distance in the range of about 20 nm toabout 70 nm, or in the range of about 30 nm to about 50 nm, althoughother depths are also contemplated.

FIG. 13 is a cross-sectional side view showing exposed vertical finsafter removal of the filler layer, protective spacers, and hardmaskcaps, in accordance with an embodiment of the present invention.

In one or more embodiments, the filler layer 180, protective spacers161, and hardmask caps 141 can be removed to expose the vertical fins131 and source/drain layer 120. In various embodiments, where the fillerlayer 180, protective spacers 161, and hardmask caps 141 are all thesame material, the filler layer, protective spacers, and hardmask capscan be removed at the same time using a single selective etchingprocess. In embodiments, in which the filler layer 180, protectivespacers 161, and hardmask caps 141 are different materials, multipleselective etching processes can be used to avoid damage to the verticalfins, substrate, and source/drain layer segments 121.

In one or more embodiments, the hardmask caps 141 can be a differentmaterial from the filler layer 180 and protective spacers 161, so thehardmask caps 141 remain on the tops of the vertical fins 131 afterremoval of the filler layer and protective spacers.

In a non-limiting exemplary embodiment, the filler layer 180 andprotective spacers 161 can be silicon dioxide (SiO₂), the sacrificialplug 175 can be silicon nitride (Si₃N₄), and the hardmask caps 141 canbe silicon borocarbide (SiBC). A remote plasma assisted SiConi™ etchprovides the simultaneous exposure of a substrate to H₂, NF₃ and NH₃plasma by-products to selectively remove silicon oxide materials. Aremote O₂/N₂ discharge with limited CF₄/NF₃ can be used to selectivelyremove Si₃N₄ over SiO₂ and Si. An SF₆+O₂ etch can remove the siliconborocarbide (SiBC).

In another non-limiting exemplary embodiment, the hardmask caps 141 canbe silicon dioxide (SiO₂) and the filler layer 180 and protectivespacers 161 can be silicon nitride (Si₃N₄), where the pinch-off layer170 and sacrificial plug 175 are a different material from theprotective spacer(s) 161 and hardmask caps 141, so the pinch-off layer170 and sacrificial plug 175 can be selectively etched back.

FIG. 14 is a cross-sectional side view showing a dummy layer coveringthe vertical fins, source/drain layer segments, and forming a fill inthe isolation region trench, in accordance with an embodiment of thepresent invention.

In one or more embodiments, a dummy layer 200 can be formed on andaround the vertical fins 131 and source/drain segments 121, where thedummy layer can be an interlayer dielectric (ILD) layer or organicplanarization layer (OPL). The dummy layer 200 can be blanket depositedon the exposed surfaces of the source/drain segments 121 and verticalfins 131, and form a fill 191 at and below source/drain segments 121 inthe isolation region trench 190.

In various embodiments, the organic planarization layer (OPL) can be apolyacrylate resin, epoxy resin, phenol resin, polyamide resin,polyimide resin, unsaturated polyester resin, polyphenylenether resin,polyphenylenesulfide resin, or benzocyclobutene (BCB), that can bepatterned and developed on the source/drain layer segments 121 andvertical fins 131. The OPL can be spun onto the surface, and a CMP canbe used to provide a smooth, flat surface.

In various embodiments, the ILD layer can be silicon oxide (SiO), alow-K insulating dielectric, silicon oxynitride (SiON), carbon dopedsilicon oxide, fluorine doped silicon oxide, boron carbon nitride (BCN),hydrogen silsesquioxane polymer (HSQ), methyl silsesquioxane polymer(MSQ), methyl doped silica or SiO_(x)(CH₃)_(y) or SiC_(x)O_(y)H_(z),organosilicate glass (SiCOH), porous SiCOH, and/or combinations thereof.Excess ILD material may be etched back or removed by chemical-mechanicalpolishing (CMP). A chemical-mechanical polishing can be used to removedexcess ILD material and provide a smooth flat surface.

FIG. 15 is a cross-sectional side view showing a masking layer on an ILDlayer, in accordance with an embodiment of the present invention.

A masking layer 210 can be formed on the ILD layer, where the maskinglayer can by a lithographic resist material that can be patterned anddeveloped, as would be known in the art. A masking layer 210 may not beused on an OPL, since the OPL can be patterned and developed.

In one or more embodiments, the masking layer 210 can be patterned anddeveloped to expose portions of an underlying ILD layer, where theexposed portions of the ILD layer can be removed to expose thesource/drain segments 121.

In various embodiments, the portion of the masking layer 210 removed canexpose the underlying ILD layer at a location on an opposite side of atleast one vertical fin 131 intervening with the filled isolation regiontrench 190. In various embodiments, two or more intervening verticalfins 131 can be between the filled isolation region trench 190 and theexposed portion of the ILD layer.

In one or more embodiments, the exposed portion of the ILD layer 200 canbe removed to expose the underlying portion of the source/drain segment121. Portions of the ILD layer 200 can be on either or both sides of thefilled isolation region trench 190 to expose the underlying portions ofthe source/drain segments 121.

FIG. 16 is a cross-sectional side view showing isolation region trenchesformed into the substrate on both sides of the initial isolation regiontrench, in accordance with an embodiment of the present invention.

In one or more embodiments, an isolation region trench 192 can be formedon either or both sides of the filled isolation region trench 190, whereone or more vertical fin(s) 131 are between the filled isolation regiontrench 190 and formed isolation region trench(es) 192. The isolationregion trenches 192 can be formed using a selective etch (e.g., RIE).The isolation region trenches 192 can extend through the source/drainsegment 121 into the substrate 110 by a distance in the range of about20 nm to about 70 nm, or in the range of about 30 nm to about 50 nm,although other depths are also contemplated. In various embodiments, theisolation region trenches 192 can be the same or different depth as theisolation region trench 190.

In one or more embodiments, the isolation region trenches 192 canseparate the source/drain segments 121 into individual source/drains 123underneath one or more vertical fins 131, where the individual bottomsource/drains 123 can each form a bottom source/drain for a FinFETdevice.

FIG. 17 is a cross-sectional side view showing the isolation regiontrenches and vertical fins after removal of the ILD layer and maskinglayer or the OPL, in accordance with an embodiment of the presentinvention.

In one or more embodiments, the dummy layer 200 and masking layer 210can be removed to expose the vertical fins 131 and newly formedisolation region trenches 192, and to reopen the isolation region trench190. The OPL or ILD layer 200 and masking layer 210 can be removed usingtechniques known in the art (e.g., etching, stripping, ashing, etc.).

FIG. 18 is a cross-sectional side view showing a trench fill layer onthe vertical fins and bottom source/drains, and in the isolation regiontrenches, in accordance with an embodiment of the present invention.

In one or more embodiments, a trench fill layer 220 can be formed on thevertical fins 121 and bottom source/drains 123, and in the isolationregion trenches 190, 192, where the trench fill layer can be blanketdeposited. The trench fill layer 220 can extend above the top surfacesof the vertical fins 131.

In one or more embodiments, the trench fill layer 220 can be aninsulating dielectric material, including but not limited to, siliconoxide (SiO), silicon oxynitride (SiON), a low-K dielectric, orcombinations thereof. The low-K dielectric can be silicon carbon dopedsilicon oxide (SiOC), fluorine doped silicon oxide (SiO:F), boron carbonnitride (BCN), hydrogen silsesquioxane polymer (HSQ), methylsilsesquioxane polymer (MSQ), methyl doped silica or SiO_(x)(CH₃)_(y) orSiC_(c)O_(y)H_(z), organosilicate glass (SiCOH), porous SiCOH, and/orcombinations thereof.

In one or more embodiments, a trench fill layer 220 can be formed in thetrenches 190. The trench fill layer 220 can be formed by a conformaldeposition (e.g., ALD), a directional deposition (e.g., gas cluster ionbeam (GCIB)) or a combination thereof to avoid pinch-off and voidformation. In various embodiments, the trench fill can be formed byatomic layer deposition (ALD), molecular layer deposition (MLD),chemical vapor deposition (CVD), low-pressure chemical vapor deposition(LPCVD), plasma enhanced chemical vapor deposition (PECVD), high densityplasma chemical vapor deposition (HDPCVD), sub-atmospheric chemicalvapor deposition (SACVD), in-situ radical assisted deposition, lowtemperature oxide deposition (LTO), ozone/TEOS deposition, limitedreaction processing CVD (LRPCVD), spin-on-coating, ion beam deposition,electron beam deposition, laser assisted deposition, chemical solutiondeposition, or any combination of the methods.

FIG. 19 is a cross-sectional side view showing filled shallow trenchisolation regions in the substrate adjacent to bottom source/drains, inaccordance with an embodiment of the present invention.

In one or more embodiments, the height of the trench fill layer 220 canbe reduced, for example, by an etch-back process (e.g., RIE). The trenchfill layer 220 can be etched back to the surface of the bottomsource/drains 123, to form a shallow trench isolation (STI) region 195in each isolation region trench 190, 192. The shallow trench isolationregion(s) 195 can electrically isolate the bottom source/drains, and aFinFET device formed on the bottom source/drain from neighboring FinFETdevices.

FIG. 20 is a cross-sectional side view showing a bottom spacer and agate structure formed on each of the vertical fins, bottomsource/drains, and shallow trench isolation regions, in accordance withan embodiment of the present invention.

In one or more embodiments, a bottom spacer layer 240 can be formed onthe bottom source/drains 123 and shallow trench isolation regions 195,for example, by a directional deposition (e.g., gas cluster ion beam(GCIB)). In various embodiments, the bottom spacer layer 240 can beformed by high density plasma (HDP) deposition followed by a conformaletch, where the HDP can be partially directional to provide a thickerbottom spacer layer 240 on surfaces substantially perpendicular (e.g.,bottom source/drain surface) to the incident beam and a thinner bottomspacer layer 240 on surfaces substantially parallel to the incident beam(e.g., vertical sidewalls). The conformal etch can remove portions ofthe bottom spacer layer 240 on the sidewalls, leaving the bottom spacerlayer 240 with a reduced thickness on the horizontal surfaces.

In one or more embodiments, the bottom spacer layer 240 can be siliconoxide (SiO), silicon nitride (SiN), a silicon oxynitride (SiON), asilicon carbonitride (SiCN), a silicon boronitride (SiBN), a siliconborocarbide (SiBC), a silicon boro carbonitride (SiBCN), a boron carbide(BC), a boron nitride (BN), or combinations thereof.

In various embodiments, bottom spacer layer material that becomesdeposited on the sidewalls of the vertical fins 131 can be etched back,for example, using an isotropic etch.

In one or more embodiments, a gate structure can be formed on the bottomspacer layer 240, where the gate structure can include a gate dielectriclayer 250 formed on at least a portion of the exposed surfaces of thevertical fin 131 and a conductive gate electrode including a conductivegate fill layer 270 and optionally a work function layer 260 between thegate dielectric layer 250 and the conductive gate fill layer 270. Insome embodiments, the gate structure can further include a dielectriccap (not shown) on top of the conductive gate fill layer 270. In variousembodiments, the gate structure can be formed by self-aligned doublepatterning (SADP) or self-aligned quadruple patterning (SAQP)techniques.

In various embodiments, the gate structure may be formed by a ‘gatefirst’ process, in which layers for the gate dielectric layer 250, workfunction layer 260, and conductive gate fill layer 270 can be formed onone or more vertical fin(s) 131. A lithography mask (e.g., a photoresistlayer and/or hardmask) can be formed on the conductive gate fill layerover the one or more vertical fin(s) 131, and patterned to exposeportions of the conductive gate fill layer 270, work function layer 260,and gate dielectric layer 250 for subsequent removal. An etching process(e.g., RIE) can be utilized to remove the conductive gate fill layer,work function layer, and gate dielectric layer to expose portions of thebottom spacer layer 240 and/or bottom source/drain 123.

In one or more embodiments, a gate structure can be formed by a‘gate-last’ process. In a gate-last process, a dummy gate structure (notshown) is formed first, followed by the gate spacer, source/drain, andinterlevel dielectric. The dummy gate is then removed and replaced bythe actual gate structure. In various embodiments, the gate dielectriclayer 250 can be formed on the exposed surfaces within the void spaceformed by a gate spacer after removal of the dummy gate, and on theexposed surfaces of the vertical fin 131 within the void space. A workfunction layer 260 can be formed on the gate dielectric layer 250. Aconductive gate fill layer 270 can be formed in the remaining void spaceafter formation of the gate dielectric layer and work function layer.

In various embodiments, the gate dielectric layer 250 can includesilicon oxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON),boron nitride (BN), high-k dielectric materials, or a combination ofthese materials. Examples of high-k dielectric materials include, butare not limited to, metal oxides such as hafnium oxide (HfO), hafniumsilicon oxide (HfSiO), hafnium silicon oxynitride (HfSiON), lanthanumoxide (LaO), lanthanum aluminum oxide (LaAlO), zirconium oxide (ZrO),zirconium silicon oxide (ZrSiO), zirconium silicon oxynitride (ZrSiON),tantalum oxide (TaO), titanium oxide (TiO), barium strontium titaniumoxide (BaSrTiO), barium titanium oxide (BaTiO), strontium titanium oxide(SrTiO), yttrium oxide (YO), aluminum oxide (AlO), lead scandiumtantalum oxide (PbScTaO), and lead zinc niobate (PbZnNbO). The high-kmaterial can further include dopants such as lanthanum (La) and aluminum(Al).

In various embodiments, the conductive gate fill layer 270 material caninclude doped polycrystalline silicon (p-Si) or amorphous silicon(a-Si), germanium (Ge), silicon-germanium (SiGe), a metal (e.g.,tungsten, titanium, tantalum, ruthenium, zirconium, cobalt, copper,aluminum, lead, platinum, tin, silver, or gold), a conducting metalliccompound material (e.g., tantalum nitride (TaN), titanium nitride (TiN),tantalum carbide (TaC), titanium carbide (TiC), titanium aluminumcarbide (TiAlC), tungsten silicide (WSi), tungsten nitride (WN),ruthenium oxide (RuO), cobalt silicide (CoSi), or nickel silicide(NiSi)), carbon nanotube(s) (CNTs), conductive carbon, graphene, or anysuitable combination of these materials. The conductive gate fill layermaterial can further include dopants that are incorporated during orafter formation (e.g., deposition).

In various embodiments, the gate structure (e.g., gate stack) canfurther include a work function setting layer. The work function layer260 can be a nitride, including but not limited to titanium nitride(TiN), hafnium nitride (HfN), hafnium silicon nitride (HfSiN), tantalumnitride (TaN), tantalum silicon nitride (TaSiN), tungsten nitride (WN),molybdenum nitride (MoN), niobium nitride (NbN); a carbide, includingbut not limited to titanium carbide (TiC) titanium aluminum carbide(TiAlC), tantalum carbide (TaC), hafnium carbide (HfC), and combinationsthereof.

In various embodiments, the lithography mask can be removed afterformation (e.g., etching) of the gate structures. In variousembodiments, a gate insulator cap layer can optionally be formed on theconductive gate fill layer 270, as a protective gate cap.

In one or more embodiments, the conductive gate fill layer 270 canextend above the top surfaces of the work function layer 260 and/or gatedielectric layer 250 on the top surfaces of the vertical fins 131. Theconductive gate fill layer 270 can be etched back or a CMP can be usedto reduce the height of the conductive gate fill layer 270.

FIG. 21 is a cross-sectional side view showing an ILD layer onconfigured gate structures, in accordance with an embodiment of thepresent invention.

In one or more embodiments, a mask can be formed on the conductive gatefill layer 270 and patterned to expose portions of the conductive gatefill layer to be removed. Portions of the conductive gate fill layer 270can be removed to separate the conductive gate fill layer 270 intoseparate conductive gates 275 on different sections of the work functionlayer 260 and gate dielectric layer 250. In various embodiments,portions of the work function layer can be removed to separate the gateelectrodes into two separate gate electrodes on different vertical fins131.

In one or more embodiments, the heights of the conductive gate filllayer 270, work function layer 260, and gate dielectric layer 250 can bereduced, for example, by an etch-back process (e.g., RIE) to define thegate length on each of the vertical fins 131. A portion of the verticalfins 131 can extend above the top surface of the gate structures toprovide space for formation of a top spacer layer and a top source/drainon each of the vertical fins 131.

In one or more embodiments, an ILD layer 280 can be formed on theconductive gate fill layer 270, work function layer 260, gate dielectriclayer 250, and vertical fins 131, where the ILD layer 280 can be blanketdeposited to fill the spaces between the separated gate electrodes andvertical fins. The ILD layer 280 can electrically isolate each gateelectrode from the adjacent gate electrodes.

FIG. 22 is a cross-sectional side view showing a top spacer layer on theILD layer and vertical fins, in accordance with an embodiment of thepresent invention.

In one or more embodiments, the ILD layer 280 can be partially removedto reduce the height of the ILD layer 280 to the top surface of theconductive gate fill layer 270, work function layer 260, and gatedielectric layer 250 to expose an upper portion of the vertical fins131. A portion of the ILD layer 280 can remain in the space between thegate electrodes to form an ILD plug 285 adjacent to a conductive gate275.

In one or more embodiments, a top spacer layer 290 can be formed on theILD plugs 285, where the can be formed by a conformal deposition (e.g.,ALD), a directional deposition (e.g., gas cluster ion beam (GCIB)) or acombination thereof. In various embodiments, top spacer layer materialthat becomes deposited on the sidewalls of the vertical fins 131 can beetched back, for example, by an isotropic etch or RIE.

In one or more embodiments, a top spacer layer 290 can be silicon oxide(SiO), silicon nitride (SiN), a silicon oxynitride (SiON), a siliconcarbonitride (SiCN), a silicon boronitride (SiBN), a silicon borocarbide(SiBC), a silicon boro carbonitride (SiBCN), a boron carbide (BC), aboron nitride (BN), or combinations thereof.

In various embodiments, an upper portion of the vertical fins 131extends above the top surface of the top spacer layer, so a portion ofthe vertical fins is exposed for formation of a top source/drain.

FIG. 23 is a cross-sectional side view showing top source/drains formedon the upper portion of the vertical fins, in accordance with anembodiment of the present invention.

In one or more embodiments, top source/drains 300 can be formed on eachof the vertical fin 131, where the top source/drains 300 can beepitaxially grown on the exposed surfaces of the vertical fins 131 abovethe top spacer layer 290. In various embodiments, the source/drains 300can be in-situ doped (where doping and epitaxy growth are performed atthe same time), and/or ex-situ doped (where doping occurs before and/orafter epitaxy). Dopants can be incorporated during epitaxy (e.g., byin-situ epitaxy) or by any other suitable doping techniques, includingbut not limited to, ion implantation, gas phase doping, plasma doping,plasma immersion ion implantation, cluster doping, infusion doping,liquid phase doping, solid phase doping, etc. In various embodiments,the source/drains 300 can be doped to form n-type or p-typesource/drains to fabricate NFETs or PFETs, where the doping of the topsource/drains 300 can be the same as the bottom source/drains 123.

In one or more embodiments, the epitaxial source/drains 300 can besilicon, silicon germanium, germanium, carbon doped silicon, carbondoped silicon germanium, or any other suitable semiconductor material.The source/drains 300 can be single crystal grown on single crystalvertical fins 131.

In a non-limiting exemplary embodiment, the source/drain 300 can beepitaxially grown on the exposed surfaces of a strained, crystalline Sior SiGe vertical fin 131 having a predetermined crystal orientation,where the source/drain(s) 300 can be formed on the three exposedsurfaces of the vertical fin 131.

In one or more embodiments, the epitaxially grown top source/drains 300can have a diamond shape, a rectangular shape, as well as other shapesdepending upon the crystal faces of the vertical fin 131 that the topsource/drain is grown on. In various embodiments, the source/drains 300can be grown until the top source/drains reach a predetermined size,where the top source/drains on the vertical fins 131 that are furtherapart by distance, D₂, remain separate unmerged top source/drains 300,and the top source/drains on the closer vertical fins that are separatedby distance, D₁, coalesce to form merged top source/drains 301. Thepredetermined size of at least two adjacent top source/drains 300 can begreater than the distance between the two adjacent vertical fins 131 toform a merged top source/drain 301, where each top source/drain spans atleast half the distance between the vertical fins 131.

The portion of the vertical fin 131 between the top source/drain 300 andbottom source/drain 123 can form a channel of a FinFET, where thecurrent would flow perpendicular to the plane of the substrate 110 fromone source/drain to another (e.g., a vertical FinFET) passed the gatestructure. The gate structure can control the amount of current flowingthrough the channel of the FinFET device.

FIG. 24 is a cross-sectional side view showing a second ILD layer formedon the top source/drains and top spacer layer, in accordance with anembodiment of the present invention.

In one or more embodiments, a second interlayer dielectric (ILD) layer310 can be formed on and around the top source/drain 300 and on the topspacer layer 290, where the ILD layer 310 can be blanket deposited onthe exposed surfaces.

In various embodiments, the ILD layer 310 can be silicon oxide (SiO), alow-K insulating dielectric, silicon oxynitride (SiON), carbon dopedsilicon oxide, fluorine doped silicon oxide, boron carbon nitride (BCN),hydrogen silsesquioxane polymer (HSQ), methyl silsesquioxane polymer(MSQ), methyl doped silica or SiO_(x)(CH₃)_(y) or SiC_(x)O_(y)H_(z),organosilicate glass (SiCOH), porous SiCOH, and/or combinations thereof.Excess ILD material may be etched back and/or removed bychemical-mechanical polishing (CMP) to provide a smooth flat surface.

In one or more embodiments, a masking layer can be formed on the ILDlayer 310, and patterned to expose portions of the ILD layer, as wouldbe known in the art. The exposed portions of the ILD layer 310 can beremoved, for example, by a directional etch (e.g., RIE) to form openingsdown to the top source/drains 300, and bottom source/drains 123. Removalof the portions of the ILD layer 310 can form vias for electricalcontacts to the FinFET device components.

In various embodiments, the vias in the ILD layer 310 can be alignedwith the unmerged top source/drains 300, and conducting material can bedeposited in the vias to form the electrical contacts 320. In variousembodiments, vias are not formed to the merged top source/drain 301.Instead, the merged top source/drain 301 creates an electricalconnection between the two neighboring vertical fins 131 and the FinFETdevices that they form a part of. A chemical-mechanical polishing can beconducted to remove excess electrical contact material and provide asmooth, flat surface.

The electrical contacts 320 can be a conductive material, including butnot limited to tungsten, titanium, tantalum, ruthenium, zirconium,cobalt, tantalum nitride, titanium nitride, cobalt silicide, nickelsilicide, carbon nanotube, conductive carbon, graphene, or any suitablecombination of these materials. The conductive material can furtherinclude dopants that are incorporated during or after deposition.

In various embodiments, the FinFET device can have a strained channelformed by the strained vertical fin 131 and a self-aligned isolationregion (e.g., shallow trench isolation (STI)) 195 formed by the trenchfill 220 adjacent to the semiconductor device and in the substrate. Anactive gate structure can be over and around the FinFET channel, anddummy gate structures can be on the ends of the vertical fin.

In one or more embodiments, an adjoined pair of vertical fin devices(e.g., FinFETs) can be formed on a substrate, where a first bottomsource/drain 123 is separated from a second bottom source/drain 123 by ashallow trench isolation (STI) region 195 formed into the substrate 110.In various embodiments, at least two vertical fins 131 can be formed oneach of the bottom source/drains 123, where the vertical fins on thesame bottom source/drain can be separated by a distance, D₂. A verticalfin 131 on the first bottom source/drain can be separated from anadjacent vertical fin 131 on the neighboring second bottom source/drainby a distance, D₁.

In one or more embodiments, a gate structure can be formed on each ofthe vertical fins 131, where a single gate structure may be on twoadjacent vertical fins and on top of the shallow trench isolation (STI)region 195. The shallow trench isolation region 195 can be self-alignedwith the one vertical fin 131 on the first bottom source/drain 123 andthe one adjacent vertical fin 131 on the neighboring second bottomsource/drain 123. In various embodiments, the shallow trench isolationregion has a width in the range of about 10 nm to about 40 nm.

In one or more embodiments, a top source/drain 300 can be formed on eachof the at least two vertical fins 131 on the first bottom source/drain123 and on the at least two vertical fins 131 on the second bottomsource/drain 123. A merged top source/drain 301 can be formed on onevertical fin 131 on the first bottom source/drain 123 and one adjacentvertical fin 131 on the second bottom source/drain 123 that bridges theshallow trench isolation region 195 to electrically couple the adjacentvertical fins. The shallow trench isolation region 195 can separate afirst fin field effect transistor device from a second fin field effecttransistor device.

In one or more embodiments, two top source/drain 300 can be epitaxiallygrown to a size that is sufficient to span the distance, D₁, between twoadjacent vertical fins 131 on separate bottom source/drains 123 to forma merged source/drain 301. The at least two vertical fins 131 on thefirst bottom source/drain 123 can form a first fin field effecttransistor device, and the at least two vertical fins 131 on the secondbottom source/drain 123 can form a second fin field effect transistordevice, where the two fin field effect transistor devices can bephysically adjoined and electrically coupled in series through themerged top source/drain 301.

In one or more embodiments, an electrical path can be formed from a topsource/drain 300 through a vertical fin 131 of a first FinFET device toa first bottom source/drain 123, through a second vertical fin to themerged top source/drain 301 to a vertical fin of a second FinFET device,through the second bottom source/drain 123 and through a second verticalfin 131 and top source/drain 300 on the second bottom source/drain 123.

In a non-limiting exemplary embodiment, an adjoined pair of vertical findevices can include a first bottom source/drain and a second bottomsource/drain on a substrate, wherein the first bottom source/drain isseparated from the second bottom source/drain by a shallow trenchisolation region in the substrate, at least four vertical fins, whereinat least two of the four vertical fins are on the first bottomsource/drain and the remaining vertical fins are on a second bottomsource/drain, a gate structure on each of the at least four verticalfins, a top source/drain on at least one of the at least two verticalfins on the first bottom source/drain, a top source/drain on at leastone of the remaining vertical fins on the second bottom source/drain,and a merged source/drain on one vertical fin on the first bottomsource/drain and one adjacent vertical fin on the second bottomsource/drain that bridges the shallow trench isolation region toelectrically couple the adjacent vertical fins.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements can also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements can be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

The present embodiments can include a design for an integrated circuitchip, which can be created in a graphical computer programming language,and stored in a computer storage medium (such as a disk, tape, physicalhard drive, or virtual hard drive such as in a storage access network).If the designer does not fabricate chips or the photolithographic masksused to fabricate chips, the designer can transmit the resulting designby physical means (e.g., by providing a copy of the storage mediumstoring the design) or electronically (e.g., through the Internet) tosuch entities, directly or indirectly. The stored design is thenconverted into the appropriate format (e.g., GDSII) for the fabricationof photolithographic masks, which typically include multiple copies ofthe chip design in question that are to be formed on a wafer. Thephotolithographic masks are utilized to define areas of the wafer(and/or the layers thereon) to be etched or otherwise processed.

Methods as described herein can be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case, the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case, the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

It should also be understood that material compounds will be describedin terms of listed elements, e.g., SiGe. These compounds includedifferent proportions of the elements within the compound, e.g., SiGeincludes Si_(x)Ge_(1-x) where x is less than or equal to 1, etc. Inaddition, other elements can be included in the compound and stillfunction in accordance with the present principles. The compounds withadditional elements will be referred to herein as alloys.

Reference in the specification to “one embodiment” or “an embodiment”,as well as other variations thereof, means that a particular feature,structure, characteristic, and so forth described in connection with theembodiment is included in at least one embodiment. Thus, the appearancesof the phrase “in one embodiment” or “in an embodiment”, as well anyother variations, appearing in various places throughout thespecification are not necessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This can be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps operations,components and/or groups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, can be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the FIGS. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the FIGS. For example, if the device in theFIGS. is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device can be otherwise oriented (rotated 90degrees or at other orientations), and the spatially relativedescriptors used herein can be interpreted accordingly. In addition, itwill also be understood that when a layer is referred being “between”two layers, it can be the only layer between the two layers, or one ormore intervening layers can also be present.

It will be understood that, although the terms first, second, etc. canbe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another element. Thus, a first element discussed belowcould be termed a second element without departing from the scope of thepresent concept.

Having described preferred embodiments of a device and fabricationmethod (which are intended to be illustrative and not limiting), it isnoted that modifications and variations can be made by persons skilledin the art in light of the above teachings. It is therefore to beunderstood that changes may be made in the particular embodimentsdisclosed which are within the scope of the invention as outlined by theappended claims. Having thus described aspects of the invention, withthe details and particularity required by the patent laws, what isclaimed and desired protected by Letters Patent is set forth in theappended claims.

What is claimed is:
 1. A method of fabricating a vertical fin fieldeffect transistor with a merged top source/drain, comprising: forming afirst vertical fin on a first bottom source/drain; forming a secondvertical fin on a second bottom source/drain, wherein the first bottomsource/drain is separated from the second bottom source/drain by ashallow trench isolation region; forming a bottom spacer layer on thefirst bottom source/drain, second bottom source/drain, and shallowtrench isolation region between the first bottom source/drain and thesecond bottom source/drain; forming a gate dielectric layer on thebottom spacer layer, the first vertical fin, and the second verticalfin; forming a first conductive gate on the gate dielectric layer; andforming a merged top source/drain on the first vertical fin and thesecond vertical fin, wherein the merged top source/drain forms anelectrical connection between the first vertical fin and the secondvertical fin.
 2. The method of claim 1, further comprising forming a topspacer layer on the first conductive gate.
 3. The method of claim 2,further comprising forming an interlayer dielectric (ILD) layer on themerged top source/drain and top spacer layer.
 4. The method of claim 3,further comprising forming a work function layer on the gate dielectriclayer.
 5. The method of claim 3, further comprising forming a thirdvertical fin on the first bottom source/drain, and a fourth vertical finon the second bottom source/drain.
 6. The method of claim 5, furthercomprising forming a top source/drain on each of the third vertical finand the fourth vertical fin, and forming an electrical contact to eachtop source/drain.
 7. The method of claim 5, wherein the distance betweenthe first vertical fin and the second vertical fin is in a range ofabout 10 nm to about 40 nm.
 8. The method of claim 7, wherein thedistance between the first vertical fin and the third vertical fin is ina range of about 30 nm to about 100 nm.
 9. The method of claim 8,further comprising forming the gate dielectric layer on the thirdvertical fin and the fourth vertical fin, and a second conductive gateon the gate dielectric layer.
 10. A method of fabricating a vertical finfield effect transistor with a merged top source/drain, comprising:forming a first vertical fin on a first bottom source/drain; forming asecond vertical fin on a second bottom source/drain, wherein the firstbottom source/drain is separated from the second bottom source/drain bya shallow trench isolation region, and wherein the distance between thefirst vertical fin and the second vertical fin is in a range of about 10nm to about 40 nm; forming a bottom spacer layer on the first bottomsource/drain, second bottom source/drain, and shallow trench isolationregion between the first bottom source/drain and the second bottomsource/drain; forming a gate dielectric layer on the bottom spacerlayer, the first vertical fin, and the second vertical fin; forming afirst conductive gate on the gate dielectric layer; and forming a mergedtop source/drain on the first vertical fin and the second vertical fin,wherein the merged top source/drain forms an electrical connectionbetween the first vertical fin and the second vertical fin.
 11. Themethod of claim 10, further comprising forming a third vertical fin onthe first bottom source/drain, and a fourth vertical fin on the secondbottom source/drain.
 12. The method of claim 11, further comprisingforming a top source/drain on each of the third vertical fin and thefourth vertical fin, and forming an electrical contact to each topsource/drain.
 13. The method of claim 12, wherein the top source/drainsare epitaxially grown on each of the at least four vertical fins. 14.The method of claim 13, further comprising forming the gate dielectriclayer on the third vertical fin and the fourth vertical fin, and asecond conductive gate on the gate dielectric layer.
 15. The method ofclaim 14, wherein the shallow trench isolation region has a width in therange of about 20 nm to about 30 nm.
 16. A method of fabricating avertical fin field effect transistor with a merged top source/drain,comprising: forming a bottom spacer layer on the first bottomsource/drain, second bottom source/drain, and shallow trench isolationregion between the first bottom source/drain and the second bottomsource/drain, wherein a first vertical fin is on the first bottomsource/drain and a second vertical fin is on the second bottomsource/drain; forming a gate dielectric layer on the bottom spacerlayer, the first vertical fin, and the second vertical fin; forming afirst conductive gate on the gate dielectric layer between the firstvertical fin and the second vertical fin; and forming a merged topsource/drain on the first vertical fin and the second vertical fin,wherein the merged top source/drain forms an electrical connectionbetween the first vertical fin and the second vertical fin.
 17. Themethod of claim 16, wherein there is a third vertical fin on the firstbottom source/drain and a fourth vertical fin on the second bottomsource/drain.
 18. The method of claim 17, further comprising forming thegate dielectric layer on the third vertical fin on the first bottomsource/drain and the fourth vertical fin on the second bottomsource/drain.
 19. The method of claim 18, forming a second conductivegate on the third vertical fin and a third conductive gate on the fourthvertical fin.
 20. The method of claim 19, forming an ILD plug betweenthe first conductive gate and the second conductive gate.